Process for partial oxidation of gaseous hydrocarbons



Aug. 9, 1932.

W. K. LEWIS PROCESS FOR PARTIAL OXIDATION OF GASEOUS HYDROGARBONS Filed March 2l, 1928 mw mm llllAI VH IVI MRREN K, Lewis @Eng 22s @1f/tom Patented Aug. 9, 1932 UNITED STATES PATENT OFFICE WARREN K. LEWIS., F NEWTON, MASSACHUSETTS, ASSIGNOR T0 STANDARD OIL DE- VELOPMENT COMPANY, A CORPORATION OF DELAWARE PROCESS FOR PARTIAL OXIDATION OF GASEOUS HYDROCARBONS Application lred March 21, 1928.VV Serial No. 263,409.

The present invention relates to the art of treating hydrocarbon materials to form valuable liquid products and more specifically to an improved process for oxidation of hydrocarbons with air to form alcohols, aldehydes, acids and other oxygen-containing products. My process will be fully understood from the following description and the drawing which illustrates one form of apparatus suitable for the process.

The drawing is a semi-diagrammatic view in elevation ot an apparatus constructed according to my invention and indicates the iiow of material through the apparatus.

y In a previous application, Serial No. 190, 728 filed May 12, 1927 by 1V. K. Lewis and P. K. Frolich and in a second application Serial No. 226,076, filed October 14, 1927 by P. K. Frolich, an oxidation process for obtaining normally liquid oxidation products such as alcohols, aldehydes, acids and other oxygen-containing compounds was disclosed. The use of air for oxidation of'hydrocarbons is economically advantageous because of its availability and it is also highly advantageous to recirculate unoxidized hydrocarbon through a zone of oxidation if one is to obtain large yields. The present invention com/ prises an improved method for oxidizing hydrocarbon by means of air and separa-ting the unoxidized hydrocarbon from residual products whereby the hydrocarbon may be economically recirculated.

Referring to the drawing, the reference character 1 designates a high pressure source of hydrocarbons which may be natural or artificial hydrocarbon gas, a single pure compound, or a hydrocarbon-containing mixture. This raw material, which will hereafter be termed hydrocarbon, is fed by a pipe 2 to a manifold 3 and then to a plurality of coils a, b, c, and d, which are carefully distributed throughout the interior of the reactor 4 and in which the hydrocarbon is preheated. The reactor may be of any suitable design but is preferably a heavy steel shell adapted. to withstand pressures in excess of 3.000 lbs. per square inch and a temperature of 600 C. or higher. The reactor is suitably lagged and may be fitted with other heat exchanging coils to absorb the heat evolved by oxidation and to 6 maintain all parts of' the reactor at approximately the same temperature, which is predetermined and called the reactor temperature. Part of' the hydrocarbon is passed by line E through a heat exchanger F and is preheated by hot products from the reactor 4. i The preheated hydrocarbon is passed to ai manifold 5 and is thence conducted to a coil 6, wherein the hydrocarbon is heated to a temperature somewhat below that of the reactor and is then discharged into a mixing pipe 7. A by-pass line 6a is provided so that all or part of the hydrocarbon may be shunted around the coil G after the reactor has reached its proper temperature. Airis compressed by a suitable compressor 8 and is also discharged into mixing pipe 7, wherein it is thoroughly mixed with the hydrocarbon. The mixture is then discharged into the reactor 4 and the heat of reaction im- 80 f mediately raises the temperature to the predetermined degree. If desired, part of the air may dow through pipe 9 and a plurality of branch pipes a', b, and c in regulated ,if quantities. g5 The mixture Jfrom the reactor is discharged ,f

into exchanger F, then into a cooler 10 and through a valve 11 into the middle of a/ rectifying tower 12 which is fitted with cooling coil 13 and heating coil 14 in its upper 9e and lower portions respectively. The liquid flowing from the base of tower 12 consists of the normally liquid oxygen-containing products and hydrocarbons, such as propane and heavier hydrocarbons, although ethane may be included, if desired. This mixture flows through line 15 and the reduction valve 16 into a second tower 17 which is fitted with cooling and heating coil 18 and 1f) as will be understood. The major quantity of the ITT;

normally liquid oxygen-containing products is obtained as liquid from the base of tower 17 and is conducted to storage (not shown) through line 20 and cooler 21.

Vapor from the top of tower 17 is conducted to a condenser 23 by line 22 and is condensed therein to a liquid preferably under pressure. The liquid which may contain small quantities of oxygen-containing products may then be conducted by line 24 to scrubbing system comprising a tower 25. Hydrocarbon is admitted at the base of tower 25 by a spray pipe 26' and a solvent, immiscible therewith and having a greater density than the hydrocarbon is admitted at the top through spray 27. In making its way to the bottom the solvent extracts the oxygen-containing products and flows through pipe 28 to tank 29. Solvent may be recirculated through line 31 by pump 30 and fresh or stripped solvent is admitted by line 32. The rich solvent may be drawn from tank 29 throu h a line 433 to stripping stills (not shown) for recovery of the oxidation products, as will be readily understood. Hydrocarbon fiows from tower 25 by line 34 and is pumped by pump 35 to the source 1 for recirculation.

Fixed gas which is discharged from the top of tower 12 by line 36, comprises methane, ethane, nitrogen and carbon dioxide and is conducted. to a scrubbing tower 37. An alkaline solution such as aqueous caustic soda is admitted by spray pipe 38 and in running down through the tower absorbs the carbon dioxide. The solution may be recirculated by lines 39 and 42 and` pump 41. Spent soda may be withdrawn from the tank 40 by line 44 and fresh soda admitted to the system b 43.

yThe gas now free of carbon dioxide flows by line 45 to a heat recuperator system indicated-generally at 46 in which the mixture is partially liquefied. The recuperatorsystem may be in any advantageous form adapted for the efficient cooling of incoming materials by the cold effluent fluids, and is preferably arranged to take advantage of counter-flow principles. Irecooled and partially liquefied mixture of nitrogen and hydrocarbon flows from recuperator 46 then flows by line 47 to a coil 48 which is submerged in the liquid, in a still 49. The still is fitted by a tower 50 into which the partially liquefied mixture is discharged by line 51 fitted with an expansion valve R. The mixture is rectified in tower 50 and the vapor fraction, com prising substantially nitrogen, escapes by vapor line 52 to recuperator system 46 and thence by line 5.3 to be discarded by line 54. A part of this nitrogen is recompressed by compressor 55 and after cooling in a cooler 56 is conducted to the recuperator 46 by lino 57. The gas is partially liquefied in 46 and passes by line 58 to coil 59 which is submerged in the liquid in still 49. From coil 59 the liquid is conveyed to the top of tower 50 by line 60 Where it serves as refiux in effecting rectification afterexpansion throughvalve R. Hydrocarbon, substantially free of nitrogen, comprising methane, ethane and propane, is withdrawn from still 49 by line 61 and after passing through recuperator 46, 1t is returned by line 62 to booster 63 and by line 64 to the source of hydrocarbon for recirculation through the system.

In the previous applications above mentloned, the conditions for oxidations have been fully disclosed and it is sufficient to say' that the reactor 4 is maintained at temperatures between 350 and 600o C. and under pressure preferably between 1500 and 3500 lbs. per square inch. The mixture of h drocarbon and air is passed at a high rate of ow preferably over a catalyst, for example, metallic nickel, in the reactor and the mixture is discharged into tower 12 for separation into liquid and gas. Pressure prevailing in 12 shall be below critical pressure of the liquid mixture boiling in base and preferably below 500 lbs. per square inch. Temperature at top of tower 12 is such that butano will be condensed and may be such that propane is reluxed as will be understood. In this manner substantially all of t-he hydrocarbons heavier than propane may be obtained as a liquid from the base of tower 12 and propane may be included in the liquid, if desired, or in the vapor or in both liquid and vapor. I contemplate operation in either of these manners, but prefer to include propane in the gas from tower. 12 since otherwise low temperature is necessary at coil 13 and must be produced by refrigeration, asis apparent.

Pressure may be reduced at valve 16 and preferably only sufficient pressure is held on tower 17 to insure that the hydrocarbon will be condensed by the cooling medium in cooler` 23, such pressure may be between atmospheric and lbs. per square inch and will vary according to the composition of the hydrocarbon feed as will be understood.

The solvent used in scrubber 25 is preferably an oxygenated solvent or one containing an hydroxyl group, such as water, methyl alcohol, ethyl alcohol, glycerine or ethylene glycol, or mixtures of such solvents with eacl other or with other substances.

The liquefaction system illustrated is similar to that known as the Linde system although other methods of liquefaction may be used as will be understood. Pressure in tower 50 is preferably above atmospheric and temperature is below the critical temperature of methane so that methane may be obtained substantially free from nitrogen, which passes from the tower by line 52 as indicated above. Operation of the liquefaction system is well known and further details need not be given.

I prefer to operate my system so that substantially no methane will be introduced into tower 17 and so that hydrocarbons heavier than propane will not go to the liquefaction system. If propane be present in a mixture with methane, ethane and higher h drocarbons, the propane is treated prefera ly with methane and ethane in the liquefaction system or it may be included wit-h the higher hydrocarbons in the subsequent distillation for separation of the oxygen-containing products. My process is Well adapted tor use with a starting material, such as natural or artificial hydrocarbon gas and if the quantity of hydrocarbon lower than ethane is small, they need not be recirculated and tower 17 and 25 may be omitted.

My process is not to be limited by any theory of the mechanism of the oxidation or by any specific example given merely by way of illustration but only by the attached claims in which I wish to claim all novelty inherent in the invention.

I claim:

4l. A process for the treatment of normally gaseous hydrocarbon mixtures to form normally liquid oxygen-containing products, comprising thefsteps of passing gaseous hydrocarbons and air under high pressure and elevated temperature into a zone of partial oxidation, passing the resulting products from said zone of partial oxidation and reducing the temperature whereby liquid and Vapor phases are produced, reducing the pressure and rectifying the mixture'to yield a gas containing nitrogen of the airvand hydrocarbons including methane and propane, and a liquid comprising normally liquid oxygenated products, cooling said gas under pressure to a temperature suiiiciently low to liquefy the greater part of the methane, rectifying the 'liquefied gas to produce nitrogen gas sub-k stantially free from hydrocarbon gas and liquid, returning the-hydrocarbon to the process and separately withdrawing nitrogen.

2. In a process according to claim 1, the steps of partially liquefying the vapor comprising gaseous hydrocarbon and nitrogen by expansion, separating /vapor from liquid so produced, recompressing residual vapor and re-expanding it for additional liquefaction.

3. Process according to claim 1 in which the vapor comprising gaseous hydrocarbon and nitrogen is scrubbed free of carbon dioxide prior to partial liquefaction. l

WARREN K. LEWIS. 

